Background. Pseudomonas aeruginosa (PA)-induced keratitis is one of the most common and destructive of bacterial diseases, ultimately culminating in blindness. This opportunistic, Gram-negative organism is best known to cause bacterial keratitis in extended contact lens wearers. In the United States alone the incidence of microbial keratitis is 25,000-30,000 cases annually with cost of treatment estimated at $15-30 million. Objective/Hypothesis. This sight-threatening disease is in large part a consequence of the inflammatory response invoked by the host, which depends on the regulation of immune cells, balance between pro- and anti-inflammatory factors released by these cells and the microenvironment, and effective restoration of tissue homeostasis. In this regard and in light of increasing incidence of antibiotic resistance, vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, has been implicated as a potent endogenous immunomodulator that affects the immune response in an anti-inflammatory manner. The goal is to delineate the VIP-induced pro-resolving mechanisms of inflammation and innate immunity using a murine model of corneal infectious disease. Furthermore, initiate pre-clinical studies for VIP as a therapeutic treatment for corneal infectious disease. Specific Aims. This proposal intends to: 1) ascertain the effects of VIP regarding expression/activation of specialized pro-resolving mediators (SPMs) of inflammation; 2) examine how VIP influences ? T cells and the production of IL-17 in driving inflammatory resolution; and 3) establish the efficacy of VIP treatment as a clinically relevant therapy for bacterial keratitis against multiple strains of PA. Study Design. Ocular infection will be induced as follows: the right eye of each animal will be scarified, and a 5 mL aliquot containing 1 x 106 CFU PA will be topically applied to the wounded corneal surface. Disease response and mechanisms of resolution will be compared between experimental (VIP-treated B6 mice) and control (PBS-treated B6 mice and PBS-treated BALB/c mice) animals using a number of well-established techniques to assess the activation state of immune cells, expression and activation of lipid mediators (lipoxins, resolvins, protectins), and other parameters of inflammation. In addition, studies will be carried out to establish pre-clinically relevant treatment modalities for VIP (e.g., modes of drug delivery, initiation of treatment post-infection, efficacy against cytotoxic and invasive strains of PA). Impact. The project examines therapeutically how interactions between the immune and neuroendocrine systems play an essential role in the resolution of ocular infection and subsequent preservation of the visual nervous system and visual acuity. In particular, the proposed studies will establish a solid basis of pre-clinical relevance to human treatment of bacterial keratitis.